The present invention relates to a charge storage device and in particular to a flexible charge storage device.
The invention has been developed primarily as a supercapacitor and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to this particular field of use and is also suitable for other energy storage devices such as batteries, capacitors and the like.
Known supercapacitors and other energy storage devices are provided in rigid containers or housings. These containers, particularly for supercapacitors offering large amounts of charge storage, are often fixedly mounted to other structures of the circuit or apparatus to which they are incorporated. The containers are generally bulky and necessitate prefabricated mounting points within the circuit or apparatus. Consequently, such circuits and apparatus do not easily accommodate a supercapacitor of differing dimension. In the event such a circuit requires a supercapacitor having different characteristics from that which was originally intended, the dimensions of the new capacitor must be very similar to the original.
It is an object of the present invention, at least in the preferred embodiments, to overcome or substantially ameliorate one or more of the disadvantages of the prior art, or at least provide a useful alternative.
According to a first aspect of the invention there is provided a flexible charge storage device including:
a first sheet electrode having a first terminal extending therefrom;
a second sheet electrode disposed adjacent the first electrode and having a second terminal extending therefrom;
a porous separator disposed between the electrodes; and
a sealed package for containing the electrodes, the separator and an electrolyte, whereby the terminals extend from the package to allow electrical connection to the respective electrodes.
Preferably, each of the sheets includes two opposed sides, at least one of the sides of each sheet having a coating containing activated carbon.
Preferably also, the first electrode and the second electrode include respective first and second aluminium sheets. More preferably, the first and second sheets and the intermediate separator are together folded.
In a preferred form the charge storage device includes a plurality of first and second sheets and intermediate separators. More preferably, the sheets and intermediate separators are stacked. Alternatively, the sheets and the intermediate separators are wound together.
Preferably also, one of the length and breadth of the package is less than the respective length and breadth of the first sheet.
Preferably, the package includes a plurality of layers. More preferably, the layer of the package closest to the terminals is polyethylene. Even more preferably, the package is sealingly bonded to the terminals. Most preferably, the package is adhesively bonded to the terminals.
In a preferred form, the package includes polyethylene and the terminals are aluminium, wherein the adhesive bond is formed with an adhesive resin. In other embodiments use is made of an epoxy resin. In other preferred embodiments each terminal includes a respective plastics sleeve sealingly bonded thereto. In this embodiment the package is preferably sealingly engaged with the sleeves. In further embodiments a plastics layer is used in place of the sleeve.
Preferably, the sheets are abutted against the separator.
In a preferred form the device, when maintained at 80xc2x0 C. for 100 hours, retains at least 90% by weight of the electrolyte. Even more preferably, and under the same conditions, the device retains at least 95% by weight of the electrolyte.
According to a second aspect of the invention there is provided a method of producing a flexible charge storage device, the method including the steps of:
providing a first sheet electrode having a first terminal extending therefrom;
disposing a second sheet electrode adjacent the first electrode, the second electrode having a second terminal extending therefrom;
disposing a porous separator between the electrodes; and
sealing the electrodes and the separator in a package containing an electrolyte, whereby the terminals extend from the package to allow electrical connection to the respective electrodes.
Preferably, each of the sheets includes two opposed sides, and the method includes the further step of applying a coating containing activated carbon to at least one of the sides of each sheet.
Preferably also, the first electrode and the second electrode are respective first and second aluminium sheets. More preferably, the method includes the step of folding together the first and second sheets and the intermediate separator.
In a preferred form, the method includes the step of providing a plurality of first and second sheets and intermediate separators. More preferably, the method includes the step of stacking the sheets and intermediate separators. Alternatively, the method includes the step of winding together the sheets and the intermediate separators.
Preferably, the package includes a plurality of layers. More preferably, the layer of the package closest to the terminals includes polyethylene. In some embodiments that layer is coated with an ionomer and more preferably coated with SURLYN. Even more preferably, the method includes the step of sealingly bonding the package to the terminals. Most preferably, the method includes the step of adhesively bonding the package to the terminals.
Preferably also, the package includes polyethylene and the terminal is aluminium, wherein the method includes the step of forming the adhesive bond with a resin. Examples of commercially available and suitable resins are those which are marketed under the names NUCREL and PRIMACOR. In other embodiments use is made of an epoxy resin. In further embodiments the method includes the steps of sealingly bonding a respective plastics sleeve to each terminal and then sealingly engaging the package with the sleeves.
In a preferred form the method includes the step of abutting the sheets against the separator.